Various types of equipment which produce digitally encoded audio data are in widespread use at present, such as apparatus for playback of digitally encoded data from compact audio discs. It is possible to implement signal level indication means for such equipment by displaying the level of the analog audio signal which is produced by analog-to-digital conversion of the digitally encoded audio data, i.e. to utilize a conventional type of audio level display apparatus, utilizing meters for example. However such level indication means cannot accurately and rapidly follow rapid changes in the audio signal level, and a much more rapid and accurate indication of the level of digitally encoded audio data can be provided by indicating the logical states of the bits constituting the digital data, prior to A-D conversion. This can be done, for example, by using an array of LED elements to display the respective bit states. However it has been found that such direct display of the digitally encoded audio data does not provide an optimum degree of display clarity to the user, so that changes in audio signal level may not be readily comprehended, due to the rapidity of changes in display state of the indicating elements. That is to say, the indicating elements will change in accordance with the frequency at which the original audio signal was sampled in order to produce the digitally encoded audio data.
It is possible to produce some improvement of the display quality by providing means for periodically latching the bits of the digitally encoded audio data at a lower frequency than that of the original sampling frequency, to thereby effectively reduce the rate at which the displayed data will change. However this has the disadvantage if the repetition frequency of the latching operations is made sufficiently low to provied an improvement in display quality, it is found that rapid changes in the audio data, and in particular rapidly changing peaks in signal amplitude, cannot be accurately followed by the level display.